1. Field of the Invention
The present invention relates to the manufacture of railroad wheels, and more particularly to the forming of bores in the hubs of railroad wheels through which axles may be received.
2. Description of the Prior Art
Steel railroad wheels have traditionally been made by casting the wheels. As part of the production of such cast steel railroad wheels, it has been necessary to form a bore in the central hub of the wheel so that the end of an axle may be inserted through the hub bore to mount the wheel on the axle. The hub bores have been formed through cutting with a torch followed by machining. Since the hub may be on the order of 6-8 inches in thickness, cutting the hub bore through this thickness of steel may take some time, and this operation typically comprises a bottleneck in the production of the wheels. Accordingly, it has been necessary to remove the wheels from the production conveying line for cutting the hub bores.
One prior art system for cutting the hub bores has used a rotating lift assembly to remove a wheel from a conveyor line and place the wheel at a hubcutting station. The railroad wheel is centered using opposed hydraulic cylinders and rotatable bearing rollers to force the railroad wheel into the desired position. The railroad wheel has a hollow steel pipe in the center of its hub. A torch assembly is then pivoted about a horizontal axis down into position over the railroad wheel. The torch assembly has a cutting torch attached to a rotatable mechanism. The lit cutting torch is positioned at the center of the railroad wheel hub with its flame traveling down the hollow steel pipe in the center of the railroad wheel hub. After the torch has pre-heated the underlying material, the torch begins cutting. The torch cuts through the railroad wheel hub in a radial direction to a pre-determined hub bore radius, and then moves around a circular path to cut the entire hub bore. When cutting is complete, the hub center should fall free from the torch-bored wheel. The torch assembly is pivoted up out of position and the railroad wheel is then placed back on the conveyor line by the rotating lift assembly, which places another railroad wheel in position at the torch cutting assembly mechanism.
The prior art hub cutting method and system has been deficient in several respects. The existing drive mechanism for the torch uses both a linear drive for the initial radial cut outward from the center of the wheel to a ring gear, and a circumferential drive that engages and drives the torch around the circumference of the ring gear to complete the cut. The drive train for both the linear and circumferential drives consists of a motor, gearbox and chain drive connected to the axis of motion. As the chain may wear and stretch over time, there may be problems with repeatably positioning the torch for the production of many wheels.
For the necessary rotary motion of the torch, the prior art has relied upon a rack and pinion arrangement connected to the chain drive and attached to the ring gear that must be lubricated. But in this environment, the hot railroad wheels may be on the order of 850 degrees F. at this point in the process. Radiant heat from the railroad wheels may tend to cause the lubricating grease to congeal, creating problems with the meshing of the gears. If the gears are not properly meshed, the torch may jump and gouge the railroad wheel, which may require scrapping the wheel if the gouge is deep enough.
In addition, the hub center does not always fall free from the railroad wheel after the hub cut is complete. It has sometimes been necessary for an operator to strike the hub center with a device such as a sledgehammer to free the hub center from the remainder of the wheel after cutting. Such a manual operation not only further slows down the manufacturing process but also may be hazardous.
In addition, with the present mechanical wheel centering device, as the rollers wear, the position of the rollers must generally be adjusted to keep the wheel in the exact center of the machine with respect to the torch. Otherwise, the hub bore cuts may be off-center, which may require the railroad wheel to be scrapped.